Liquid crystal display device

ABSTRACT

In a liquid crystal display device having a flexible printed circuit board which includes a laminated structure of a pair of flexible films, a plurality of first conductive layers interposed between inner surfaces of the flexible films to be spaced from each other, and a plurality of groups of terminals formed on an outer surface of one of flexible films opposite to the respective first conductive layers, and a liquid crystal display panel which includes a plurality of groups of wirings formed on one of a pair of substrates thereof and connected to the plurality of groups of terminals respectively, the present invention interposes second conductive layers at respective portions spacing the plurality of first conductive layers between the inner surfaces of the flexible films and prevents the one of the pair of substrates from being cracked when the plurality of terminals of the flexible printed circuit board are connected to the groups of wiring of the one of the substrates by compression bonding thereby.

This application is a Continuation of nonprovisional U.S. applicationSer. No. 10/287,663 filed Nov. 5, 2002 now U.S. Pat. No. 6,734,941.Priority is claimed based on U.S. application Ser. No. 10/287,663 filedNov. 5, 2002 now U.S. Pat. No. 6,743,941, which claims the priority ofJapanese Patent Application No. 2001-343109 filed Nov. 8, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly to a liquid crystal display device which can enhancethe reliability by obviating the occurrence of cracks in a substrate ofa liquid crystal display panel when output terminals of a flexibleprinted circuit board are connected to electrode terminals of a liquidcrystal display panel by compression bonding.

2. Description of the Related Art

In a panel type display device such as a liquid crystal display device,a display region having a plurality of pixels constituted of electrodesand active elements is formed on an inner surface of an insulatingsubstrate made of glass or the like, and a flexible printed circuitboard is popularly used as connection means between driving circuits ofthe pixels and external devices such as host computers for applyingsignals and voltages for displaying (hereinafter also referred to asdisplay signals) to these pixels. Here, the explanation is made usingthe liquid crystal display device as an example, the same goes for anorganic EL display device, a field emission type cathode ray tube andthe like.

For example, in an active matrix type liquid crystal display devicewhich is currently well known as this type of panel type display device,in general, a display region having active elements such as thin filmtransistors provided for respective pixels is formed on one substrate ofa liquid crystal display panel which sandwiches liquid crystal betweentwo sheets of substrates, and a plurality of driving circuit chips whichperform switching driving of these active elements are provided on aperiphery of the substrate or in the vicinity of the periphery of thesubstrate.

Various methods have been known as modes for mounting the drivingcircuit chips on the liquid crystal display panel. One of such modes isa so-called flip chip method (hereinafter referred to as “FCA method”)which directly mounts the driving circuit chips on the periphery of thesubstrate which constitutes the liquid crystal display panel. Besidessuch a method, a method which mounts the above-mentioned driving circuitchips on the flexible printed circuit board or a method which mounts theabove-mentioned driving circuit chips on an interface substrateinterposed between the liquid crystal display panel and the externaldevice has been commercialized. In these methods, electrode terminalsare pulled out from the display region of the liquid crystal displaypanel and outputs of the driving circuit chips which apply displaysignals to these electrode terminals are connected to the electrodeterminals.

In the FCA method, the output terminals of the driving circuit chips aredirectly connected to the above-mentioned electrode terminals. Further,to panel input terminals which are formed on the glass substrate and areconnected with input terminals of the driving circuit chips, the outputterminals of the flexible printed circuit board are connected through ananisotropic conductive film by compression bonding.

In the method which mounts the driving circuit chips on the flexibleprinted circuit board or in the method which mounts the driving circuitchips on the interface substrate, the electrode terminals which arepulled out from the display region of the liquid crystal display panelare used as the panel input terminals and the output terminals of theflexible printed circuit board are connected to these panel inputterminals using the same means by compression bonding.

Further, various methods have been also proposed for supplying displaysignals and, recently, a data transfer method which sequentiallytransfers display signals with respect to a plurality of driving circuitchips mounted in the FCA method has been popularly adopted. This datatransfer method is a method which sequentially transfers driving signalsto the driving circuit chip of succeeding stage in response to thecompletion of the pixel selection operation of the driving circuit chipof preceding stage. This data transfer method reduces a burden incurredby wiring at the flexible printed circuit board side by mounting somedisplay signal paths on the substrate of the liquid crystal displaypanel.

FIG. 7A and FIG. 7B are schematic views for explaining an essential partof a liquid crystal display device in which a flexible printed circuitboard is connected to a liquid crystal display panel adopting the datatransfer method which is provided with driving circuit chips of FCAmethod. FIG. 7A is a plan view of the liquid crystal display device andFIG. 7B is a cross-sectional view taken along a line A-A′ in FIG. 7A. InFIG. 7A and FIG. 7B, reference symbol SUB1 indicates one substrate whichconstitutes a liquid crystal display panel LCD, reference symbol SUB2indicates another substrate which constitutes the liquid crystal displaypanel LCD, reference symbol CH1 indicates driving circuit chips at ascanning signal supply side (hereinafter also referred to as gatedrivers), and reference symbol CH2 indicates driving circuit chips at avideo signal supply side (hereinafter also referred to as draindrivers).

Further, reference symbol FPC1 indicates a first flexible printedcircuit board which is connected to one substrate SUB1 side on which thegate drivers CH1 are mounted and reference symbol FPC2 indicates asecond flexible printed circuit board which is connected to onesubstrate SUB1 side on which the drain drivers CH2 are mounted. Theconstitution around the wiring of the first flexible printed circuitboard FPC1 and the gate drivers CH1 of the liquid crystal display panelLCD is substantially equal to the constitution around the wiring of thesecond flexible printed circuit board FPC2 and the drain drivers CH2, sothat the constitution around the wiring of the first flexible printedcircuit board FPC1 and the gate driver CH1 of the liquid crystal displaypanel LCD is explained here.

With respect to the first flexible printed circuit board FPC1, on a basefilm BFM, a wiring pattern PTN having an input terminal portion TM whichis connected to an interface printed circuit board not shown in thedrawing and output terminals FTM which are connected to the wiringpattern PTN are formed. Here, the output terminals FTM are exposed froma cover film. Although the wiring pattern PTN is covered with the coverfilm in the same manner except for the output terminals FTM and theinput terminal portion TM (a connection portion with the interfacesubstrate) provided to an end portion of the wiring pattern PTN, theillustration of such a constitution is omitted from FIG. 7A and FIG. 7B.

The wiring pattern PTN of the first flexible printed circuit board FPC1is formed to be extended in the longitudinal direction of the firstflexible printed circuit board FPC1 from an input terminal portion TMthereof connected to an interface printed circuit board (not shown inthe drawing). Output terminals FTM of the first flexible printed circuitboard FPC1 are arranged as a plurality of groups of terminals protrudedbetween a plurality of gate drivers CH1 respectively from the regionwhere the wiring pattern PTN is formed in the direction transverse tothe wiring pattern PTN.

The output terminals FTM of the first flexible printed circuit boardFPC1 are exposed to overlap to panel inputting terminals LTM of theliquid crystal display panel LCD in an opposed manner and are connectedto the panel inputting terminals LTM using an anisotropic conductivefilm ACF. Here, the panel inputting terminals LTM which constituteinputting terminals of the driving printed circuit board are not shownin FIG. 7A. Each of terminal groups being formed of plural terminals issimply described as a terminal for convenience in this specification.

SUMMARY OF INVENTION

This compression bonding connection is performed by heating and pressingto a substrate (a first substrate SUB1) of a liquid crystal displaypanel LCD in a direction indicated by an arrow P from a back-surfaceside (a cover film CVR side in FIG. 7B) of the first flexible printedcircuit board FPC. As shown in FIG. 7A, the output terminals FTM of thefirst flexible printed circuit board FPC1 are positioned such that theyare deviated or concentrated between the driving circuit chips CH1 andare not arranged uniformly. As a result, the panel inputting terminalsLTM at the liquid crystal display panel LCD side and the outputterminals FTM at the first flexible printed circuit board FPC1 side areconnected to each other in a conductive manner. The connection state isindicated as FTM/LTM in FIG. 7A.

In performing this connection operation by compression bonding, theremay arise a phenomenon that cracks occur in the first substrate SUB1.The reason that such cracks occur is considered as follows. That is,since the arrangement of the output terminals FTM of the flexibleprinted circuit board FPC1 is not uniform, when the compression bondingconnection is performed, a stress is concentrated on connection portionsbetween the input terminals LTM at the liquid crystal display panel LCDside and the output terminals FTM at the flexible printed circuit boardFPC1 side. Particularly, this phenomenon appears noticeably in aconnection method with a small number of terminals which adopts “a datatransfer method” in which the scanning signals and the video signals aresequentially transmitted to the driving circuit chips. However, inmounting methods and connection methods other than the FCA method, asimilar phenomenon may arise depending on the arrangement state ofterminals and the number of arranged terminals. These phenomena reducesthe reliability of the liquid crystal display device and also hampersthe enhancement of the yield.

Further, besides the above-mentioned phenomena which arise at thegate-driver-side substrate, a similar phenomenon may also arise at thetime of connecting the flexible printed circuit board to the draindriver side.

Accordingly, it is an object of the present invention to provide aliquid crystal display device which can obviate the occurrence of cracksin a substrate of a liquid crystal display panel when output terminalsof a flexible printed circuit board are connected to panel inputterminals of a liquid crystal display panel by compression bonding thusenhancing the reliability of the liquid crystal display device.

According to the present invention, the above-mentioned object isachieved by providing a dummy pattern made of a conductor similar to aconductor of a wiring pattern to portions where terminals of a flexibleprinted circuit board are not arranged. Typical structures of the liquidcrystal display device according to the present invention are describedhereinafter.

Structure (1)

In a liquid crystal display device including a liquid crystal displaypanel which forms a display region by sandwiching liquid crystal betweena pair of substrates having electrodes for selection of pixels on oneinner surface or both inner surfaces thereof and has panel inputterminals at a periphery of one of the pair of substrates for applyingdisplay signals to a plurality of electrode terminals pulled out fromthe display region, and a flexible printed circuit board having amulti-layered structure which includes output terminals connected to thepanel input terminals for applying display signals to the electrodes,

the improvement is characterized in that the panel input terminals areformed of a plurality of groups of terminals which are arranged at agiven interval along the longitudinal direction of the periphery of oneof the pair of substrates,

the flexible printed circuit board includes input terminals which areconnected to an external circuit and the output terminals which areconnected to the panel input terminals, and a conductive pattern whichconnects the input terminals and the output terminals by wiring, and

at portions of the flexible printed circuit board corresponding topositions between the electrode terminals of the liquid crystal displaypanel, dummy conductive patterns which are capable of reducing thestress concentration when the output terminals of the flexible printedcircuit boards are overlap the corresponding panel input terminals ofthe liquid crystal display panel to connect by compression bonding areprovided.

Due to such a constitution, the dummy conductive pattern receives thepressing force which is applied to the overlapped portions between thepanel input terminals of the liquid crystal display panel and the outputterminals of the flexible printed circuit board when the compressionbonding is performed. Accordingly, it is possible to prevent theexcessive stress from being applied to the overlapped portion ofneighboring panel input terminal and the output terminal thussuppressing the occurrence of cracks in the substrate of the liquidcrystal display panel.

Structure (2)

In the above-mentioned constitution (1), driving circuit chips whichapply display signals to the electrode terminals are directly mounted onone substrate between the electrode terminals and the panel inputterminals.

In the data transfer method which directly mounts the driving circuitchips on the substrate of the liquid crystal display panel using the FCAmethod, the number of the panel input terminals of the liquid crystaldisplay panel and the output terminals of the flexible printed circuitboard is small compared to conventional driving methods. Accordingly,the stress concentration which is generated on the overlapped portionsbetween the above-mentioned panel input terminals and output terminalsis large. However, with the provision of the dummy conductive patternformed on the overlapped portion of the neighboring panel input terminaland output terminal, such a stress concentration can be reduced.Accordingly, the occurrence of cracks on the substrate of the liquidcrystal display panel can be suppressed.

Structure (3)

In the above-mentioned structure (1), driving circuit chips which applydisplay signals to the electrode terminals are mounted on the flexibleprinted circuit board.

Structure (4)

In the above-mentioned structure (1), the liquid crystal display deviceincludes an interface printed circuit board to which the input terminalsof the flexible printed circuit board are connected, and driving circuitchips which supply display signals to the electrode terminals aremounted on the interface printed circuit board.

In the liquid crystal display device which mounts the driving circuitchips on the flexible printed circuit board or on the interface printedcircuit board, the number of panel input terminals of the liquid crystaldisplay panel and output terminals of the flexible printed circuit boardis larger than in the liquid crystal display device which adopts the FCAmethod. However, the stress concentration which is generated on theoverlapped portions between the panel input terminals and the outputterminals when these terminals are arranged non-uniformly on design canbe reduced due to the dummy conductive pattern, so that the occurrenceof cracks on the liquid crystal display panel can be suppressed.

The above-mentioned advantageous effects can be obtained by thestructure of another liquid crystal display device according to thepresent invention which is described hereinafter.

Structure (5)

In a liquid crystal display device comprising a liquid crystal displaypanel having a display region which includes a pair of substrates, aliquid crystal layer sealed between the pair of substrates, and aplurality of pixels formed in a state that the pixels face the liquidcrystal layer, a control circuit which controls an image displayoperation performed by the plurality of pixels, and a flexible printedcircuit board which has a plurality of connection terminals which areconnected to one end portion (at least along one side of one substratewhich is projected from an end portion of the other substrate) of one ofthe pair of substrates and transfers image display control signals orvideo data (video signals) from the control circuit to the liquidcrystal display panel through the connection terminals, wherein

the flexible printed circuit board includes a trunk portion whichextends along the end portion of one substrate and a plurality of branchportions which are projected corresponding to a plurality of respective(groups of) connection terminals from the trunk portion to the endportion of one substrate;

the trunk portion and the branch portions have a laminated structurewhich is constituted of a pair of flexible films (for example, resinfilms which are referred to as a base film and a cover film) and aplurality of conductive patterns (for example, conductive layers made ofmetal or alloy) formed between the pair of flexible films correspondingto the branch portions;

the plurality of (groups of) connection terminals are formed on an outersurface (a surface at a side opposite to the conductive pattern or, inother words, an outer surface of the laminated structure) of one of thepair of flexible films such that respective groups of the plurality ofconnection terminals correspond to the plurality of branch portions; and

between the pair of flexible films, another conductive layers are formedin a spaced-apart manner such that another conductive layer is arrangedbetween a pair of neighboring conductive patterns among the plurality ofconductive patterns.

According to the structure (5), when N pieces of the branch portions areprojected from the trunk portion, (N−1) pieces of the another conductivelayers are arranged in parallel along the extending direction of thetrunk portion. The another conductive layers may be formed such that theanother conductive layers are arranged at the liquid crystal displaypanel side of the trunk portion as so-called dummy patterns which areelectrically separated from both of wiring for signal transmission andwiring for supplying electric power to the liquid crystal display panelin the flexible printed circuit board.

The present invention is not limited to the above-mentionedconstitutions and the constitutions of embodiments which will beexplained hereinafter. It is needless to say that various modificationscan be made without departing from the technical concept of the presentinvention. For example, the present invention is applied in the samemanner to the compression bonding connection between the input terminalsof the flexible printed circuit board and the output terminals of theinterface printed circuit board and the compression bonding connectionbetween the flexible printed circuit board and the hard printed circuitboard.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B are schematic views for explaining a constitutionalexample of one embodiment of a flexible printed circuit board for use ina liquid crystal display device according to the present invention,wherein FIG. 1A is a plan view and FIG. 1B is a cross-sectional viewtaken along a line A-A′ in FIG. 1A;

FIG. 2A and FIG. 2B are schematic views for explaining an essential partof one embodiment of a liquid crystal display device in which theflexible printed circuit board is connected to a liquid crystal displaypanel provided with driving circuit chips of an FCA method according tothe present invention, wherein FIG. 2A is a plan view and FIG. 2B is across-sectional view taken along a line B-B′ in FIG. 2A;

FIG. 3 is a schematic cross-sectional view for explaining an essentialpart of one embodiment of the liquid crystal display device according tothe present invention;

FIG. 4 is a schematic cross-sectional view for explaining an essentialpart of another embodiment of the liquid crystal display deviceaccording to the present invention;

FIG. 5 is a schematic cross-sectional view for explaining an essentialpart of still another embodiment of the liquid crystal display deviceaccording to the present invention;

FIG. 6 is a plan view for explaining a specific example of the liquidcrystal display device according to the present invention; and

FIG. 7A and FIG. 7B are schematic views for explaining an essential partof a liquid crystal display device in which a flexible printed circuitboard is connected to a liquid crystal display panel of a data transfermethod provided with driving circuit chips of an FCA method, whereinFIG. 7A is a plan view and FIG. 7B is a cross-sectional view taken alonga line A-A′ in FIG. 7A.

DETAILED DESCRIPTION

The preferred embodiments of the present invention are explained indetail hereinafter in conjunction with drawings showing theseembodiments. FIG. 1A and FIG. 1B are schematic views for explaining aconstitutional example of one embodiment of a flexible printed circuitboard for use in a liquid crystal display device according to thepresent invention, wherein FIG. 1A is a plan view and FIG. 1B is across-sectional view taken along a line A-A′ in FIG. 1A.

This flexible printed circuit board constitutes a first flexible printedcircuit board FPC1 which is mounted on a gate drive side of a liquidcrystal display panel. As shown in FIG. 1B, the first flexible printedcircuit board FPC1 includes a wiring pattern PTN and a dummy conductivepattern DPN at one side of a base film BFM and they are covered with acover film CVR.

At the other side of the base film BFM, output terminals FTM which areelectrically connected with the above-mentioned wiring pattern PTN areformed. As shown in FIG. 1A and FIG. 1B, the output terminals FTM arearranged irregularly or non-uniformly for every group consisting of aplurality of output terminals FTM. The dummy conductive pattern DPN isprovided between these groups of output terminals FTM. The dummyconductive pattern DPN is provided in the vicinity of a center portionof the arrangement of a group of output terminals FTM which are pressedmainly by a compression bonding tool.

FIG. 2A and FIG. 2B are schematic views for explaining an essential partof one embodiment of a liquid crystal display device in which theflexible printed circuit board is connected to a liquid crystal displaypanel provided with driving circuit chips of an FCA method according tothe present invention, wherein FIG. 2A is a plan view and FIG. 2B is across-sectional view taken along a line B-B′ in FIG. 2A. In FIG. 2A andFIG. 2B, reference symbols which are equal to the reference symbolsshown in FIG. 1A and FIG. 1B indicate parts having identical functions.The flexible printed circuit board constitutes the first flexibleprinted circuit board FPC1 explained in conjunction with FIG. 1A andFIG. 1B.

In FIG. 2A and FIG. 2B, reference symbol SUB1 indicates one substratewhich constitutes a liquid crystal display panel LCD (here, a thin filmtransistor substrate having thin film transistors as active elements),reference symbol SUB2 indicates another substrate (here, a color filtersubstrate which faces the thin film transistor substrate in an opposedmanner), reference symbol CH1 indicates driving circuit chips at ascanning signal supply side (hereinafter, referred to as a gate driver),and reference symbol CH2 indicates driving circuit chips at a videosignal supply side (hereinafter, referred to as a drain driver).

In the above-mentioned manner, reference symbol FPC1 indicates the firstflexible printed circuit board which is connected to one substrate SUB1side on which the gate drivers CH1 are mounted and reference symbol FPC2indicates the second flexible printed circuit board which is connectedto one substrate SUB1 side on which the drain drivers CH2 are mounted.The constitution around the wiring of the first flexible printed circuitboard FPC1 and the gate driver CH1 of the liquid crystal display panelLCD is substantially equal to the constitution around the wiring of thesecond flexible printed circuit board FPC2 and the drain driver CH2, sothat the constitution around the wiring of the first flexible printedcircuit board FPC1 and the gate driver CH1 of the liquid crystal displaypanel LCD is explained here.

With respect to the first flexible printed circuit board FPC1, on thebase film BFM, the wiring pattern PTN having an input terminal portionTM which is connected to an interface printed circuit board not shown inFIG. 2A and FIG. 2B and an output terminal FTM which is connected to thewiring pattern PTN are formed. Here, the output terminal FTM is exposedfrom the cover film CVR. Although the wiring pattern PTN is covered withthe cover film CVR in the same manner except for the output terminal FTMand the input terminal portion TM (a connection portion with theinterface substrate) provided to an end portion of the wiring patternPTN, the illustration of such a constitution is omitted from thedrawings.

The wiring pattern PTN of the first flexible printed circuit board FPC1is formed of a wiring pattern which has the input terminal portion TMthereof connected to an interface printed circuit board (not shown inFIG. 2A and FIG. 2B) and is extended in the longitudinal direction ofthe first flexible printed circuit board FPC1. Output terminals FTM ofthe first flexible printed circuit board FPC1 are arranged as aplurality of groups of terminals between a plurality of gate drivers CH1in the direction which crosses the wiring pattern PTN from the regionwhere the wiring pattern PTN is formed.

As mentioned previously, the output terminals FTM of the first flexibleprinted circuit board FPC1 are exposed and are to overlap the panelinputting terminals LTM of the liquid crystal display panel LCD in anopposed manner and are connected to the panel inputting terminals LTMusing an anisotropic conductive film ACF. Here, the inputting terminalTM which constitutes an inputting terminal of the driving circuit board(the first flexible printed circuit board FPC1) is not shown in FIG. 2B.In this liquid crystal display panel LCD, electrode terminals GT whichare pulled out from a display region of the liquid crystal display panelare connected to the output terminals of the gate drivers CH1, while thepanel input terminals LTM which are connected to the input terminals ofthe gate drivers CH1 are bonded by compression to the output terminalsFTM of the flexible printed circuit board FPC1 by way of a pattern (notshown in FIG. 2A and FIG. 2B) which is wired on the first substrate SUB1in the direction indicated by an arrow P.

FIG. 3 is a schematic cross-sectional view for explaining an essentialpart of one embodiment of the liquid crystal display device according tothe present invention. In this liquid crystal display device, thedriving circuit chip (driver) is mounted using the FCA method explainedin conjunction with FIG. 2A and FIG. 2B, wherein the gate driver CH1 isdirectly mounted on the periphery of the first substrate SUB1 of theliquid crystal display panel.

Input terminals of the first flexible printed circuit board FPC1 areconnected to terminal portions of an interface printed circuit boardPCB. The interface printed circuit board PCB is bent toward a backsurface of the first substrate SUB1 and is accommodated in the rearsurface of the liquid crystal display panel. The input terminals of thefirst flexible printed circuit board FPC1 and the terminals of theinterface printed circuit board PCB are also overlapped each other andare bonded by compression in the direction indicated by the arrow P.

Here, when the arrangement of the input terminals of the first flexibleprinted circuit board FPC1 is not uniform, by providing a dummyconductive pattern between the input terminals of the first flexibleprinted circuit board FPC1 in the same manner as the above-mentioneddummy conductive pattern (see DPN in FIG. 1B), it is possible tosuppress the occurrence of cracks in the interface printed circuit boardPCB.

FIG. 4 is a schematic cross-sectional view showing another embodiment ofthe liquid crystal display device according to the present invention. Inthis liquid crystal display device, the gate driver CH1 is mounted onthe first flexible printed circuit board FPC1. Accordingly, the outputterminals of the first flexible printed circuit board FPC1 are directlyconnected by compression bonding to electrode terminals formed on thefirst substrate SUB1. The compression bonding is also performed in thedirection indicated by an arrow P.

Also in this embodiment, input terminals of the first flexible printedcircuit board FPC1 are connected to terminal portions of an interfaceprinted circuit board PCB. The interface printed circuit board PCB isbent toward a back surface of the first substrate SUB1 and isaccommodated in the rear surface of the liquid crystal display panel.The input terminals of the first flexible printed circuit board FPC1 andthe terminals of the interface printed circuit board PCB are alsooverlapped to each other and are bonded by compression in the directionindicated by the arrow P.

Also in this case, when the arrangement of the input terminals of thefirst flexible printed circuit board FPC1 is not uniform, by providing adummy conductive pattern between the input terminals of the firstflexible printed circuit board FPC1 in the same manner as theabove-mentioned dummy conductive pattern (see DPN in FIG. 1B), it ispossible to suppress the occurrence of cracks in the interface printedcircuit board PCB.

FIG. 5 is a schematic cross-sectional view showing another embodiment ofthe liquid crystal display device according to the present invention. Inthis liquid crystal display device, the gate driver CH1 is mounted onthe interface printed circuit board PCB. The output terminals of thefirst flexible printed circuit board FPC1 are directly connected bycompression bonding to electrode terminals formed on the first substrateSUB1. The compression bonding is also performed in the directionindicated by an arrow P.

Also in this embodiment, input terminals of the first flexible printedcircuit board FPC1 are connected to terminal portions of an interfaceprinted circuit board PCB. The interface printed circuit board PCB isbent toward a back surface of the first substrate SUB1 and isaccommodated in the rear surface of the liquid crystal display panel.The input terminals of the first flexible printed circuit board FPC1 andthe terminals of the gate drivers CH1 which are mounted on the interfaceprinted circuit board PCB are bonded to each other by compression in thedirection indicated by the arrow P.

Also in this case, when the arrangement of the input terminals of thefirst flexible printed circuit board FPC1 is not uniform, by providing adummy conductive pattern between the input terminals of the firstflexible printed circuit board FPC1 in the same manner as theabove-mentioned dummy conductive pattern (see DPN in FIG. 1B), it ispossible to suppress the occurrence of cracks in the interface printedcircuit board PCB.

FIG. 6 is a plan view for explaining a specific example of the liquidcrystal display device according to the present invention. The firstflexible printed circuit board FPC1 is mounted on a left side (a lateraldirection side at the left in the drawing) of the liquid crystal displaypanel LCD which is formed by laminating the first substrate SUB1 and thesecond substrate SUB2. The second flexible printed circuit board FPC2 ismounted on a lower side (a longitudinal direction side at the lower sidein the drawing) of the liquid crystal display panel LCD and is foldedback toward the rear surface of the liquid crystal display panel PNLalong the arrangement of openings HOP for bending.

Further, both of the gate drivers CH1 and the drain drivers CH2 aredirectly mounted on the periphery of the first substrate SUB1. A timingconverter TCON is mounted on the interface printed circuit board PCB andvarious signals and voltages for displaying are supplied to theinterface printed circuit board PCB from an external circuit (hostcomputer) through a connector CT. The input terminal TM of the firstflexible printed circuit board FPC1 is connected to a terminal PBM ofthe interface printed circuit board PCB.

Signals supplied to the second flexible printed circuit board FPC2served for the above-mentioned displaying are supplied through wiringextending from the first flexible printed circuit board FPC1 to thefirst substrate SUB1. The first flexible printed circuit board FPC1 andthe second flexible printed circuit board FPC2 are bent toward the backsurface of the liquid crystal display panel LCD. The interface printedcircuit board PCB is also accommodated in the back surface of the liquidcrystal display panel LCD in the same manner. Here, an upper polarizerPOL1 is laminated to a display screen side (front surface of the secondsubstrate SUB2) of the liquid crystal display panel LCD and a displayregion AR is formed in the inside of the liquid crystal display panelLCD.

As has been explained heretofore in conjunction with severalembodiments, according to the present invention, it is possible toobviate the occurrence of cracks on the substrate of the liquid crystaldisplay panel at the time of connecting the output terminals of theflexible printed circuit board to the panel input terminals of theliquid crystal display panel by compression bonding so that it ispossible to provide the liquid crystal display device which can enhancethe reliability thereof.

What is claimed is:
 1. A display device, comprising: a glass substratehaving a display area where a plurality of pixels are arranged andperipheral area where a plurality of driver circuits each supplyingsignals to a corresponding group of the plurality of pixels arejuxtaposed along an edge of the glass substrate and a plurality ofgroups of input terminals each arranged between the driver circuits; anda flexible printed circuit board which has a plurality of groups ofconnection terminals each corresponding to one of the plurality ofgroups of input terminals, the respective connection terminals belongingto each of the groups electrically connected to the respective inputterminals belonging to a corresponding one of the plurality of groups ofinput terminals, wherein the flexible printed circuit board is formed ofa pair of flexible films and first conductive layers interposed betweenthe pair of flexible films, and includes a trunk portion being extendedalong the edge of the glass substrate and a plurality of branch portionseach being protruded from the trunk portion to the edge of the glasssubstrate, each of the plurality of branch portions corresponds to oneof the plurality of groups of connection terminals and has each of theconnection terminals belonging to the one of the plurality of groups ofconnection terminals formed on an outer surface of one of the pair offlexible films thereof, each of the plurality of groups of connectionterminals is connected to the corresponding one of the plurality ofgroups of input terminals with an anisotropic conductive film, each ofthe first conductive layers is extended from the trunk portion to one ofthe plurality of branch portions to oppose to one of the plurality ofgroups of connection terminals, and second conductive layers areinterposed between the pair of flexible films in the trunk portion andeach of the second conductive layers is disposed between an adjacentpair of the first conductive layers to be spaced from one another.
 2. Adisplay according to claim 1, further comprising a third conductivelayer interposed between the pair of flexible films in the trunkportion, wherein the third conductive layer is patterned together withand connected to the first conductive layers.
 3. A display deviceaccording to claim 1, wherein each of the first conductive layers iselectrically connected to the connection terminals belonging to one ofthe plurality of groups corresponding thereto.